About the BSE Sensex
The S&P BSE Sensex (Sensitive Index) is India’s oldest stock market benchmark, tracking 30 of the largest and most actively traded companies on the Bombay Stock Exchange. Launched in 1986 with a base year of 1978-79 (base value 100), it remains the most quoted single number in Indian financial media — the “Sensex” in headlines.
Methodology
The Sensex uses a free-float market capitalisation weighted methodology, identical in principle to the Nifty 50 but on a smaller 30-stock universe. The index is calculated in real time during trading hours and is rebalanced periodically by the BSE Index Committee.
Sensex vs Nifty
Despite different stock counts and exchanges, the Sensex and Nifty 50 move very closely in lockstep — correlation typically > 0.98 — because both reflect the same large-cap Indian universe. The Nifty is generally preferred by F&O traders (more liquid index futures and options) while the Sensex remains the lay public’s preferred shorthand for “the market.”
Historical milestones
- 1000: July 1990
- 10,000: February 2006
- 50,000: January 2021
- 80,000: July 2024